Air Pressure on LS440

Hie guys I'm running a Komori LS440 and of late I've noticed we having problems with air pressure. The machine runs on 6 bars but now at times i see my pressure drop to 5,5 or less. The air compressor I have been using is still the same as before we had this problem. I have checked for leaks on my machine but haven't picked up any, the compressor runs perfectly and we've checked for leaks along the pipe and none found. If I close air to my machine the air picks up on the compressor . My question is how much litres per minute does the machine consume so i can get a bigger compressor with the right capacity. I can't find that information.